With a growing density of electronic components in electronic devices, EMI (electromagnetic interference) robustness is a major specification aspect which needs to be considered during the design of an electronic component, such that the suppression of EMI injection becomes a part of the system to be designed. In automotive products, for example, suppression of EMI is very important, especially in safety related areas where EMI can influence proper operation of electronic systems thereby possibly causing human casualties.
Unfortunately, EMI suppression usually comes at the cost of additional external and internal components. Sometimes, depending on the desired specification or design restrictions of a respective electronic component, it may even be impossible to implement EMI suppression with external components, for example in the case when the integrated circuit is manufactured according to SPT9 (9th generation smart power technology) with a 130 nm manufacturing technology or according to BCDMOS (combined bipolar CMOS (complementary metal-oxide semiconductor) and DMOS (diffused metal-oxide semiconductor) technologies) technology, because the respective external components providing EMI protection are simply too big.
FIG. 1 shows a conventional circuit 100 with a RC filter that is often used to achieve EMI suppression with external components. The RC filter, which includes a resistor 104 and a capacitor 106, is coupled between a circuit input 102 and a microcontroller 108 which may for example include an ADC (analog to digital converter). An input signal applied to the circuit input 102 is thus first low pass filtered before it is fed into the microcontroller 108 via a first input of the microcontroller 108. The other input of the microcontroller 108 is coupled to a reference potential together with one side of the capacitor 106. The capacitance of the filter capacitor 106 is mostly in the range of several nanofarad and the resistance of the filter resistor 104 is on the order of kiloohms such that the corner frequency of the RC filter is typically in the range of several kilohertz. The microcontroller 108 may include a switched capacitor circuit with a capacitance in the range of a few picofarad. The sampling rate of the microcontroller 108 or the ADC which may be included therein may lie in the range of a few hundred kilohertz. The capacitance of the filter capacitor 106 may be chosen big enough such that the switched capacitor included in the microcontroller 108 can be fully charged during every sampling cycle. The signal provided at the circuit input 102 may come from a high voltage circuit manufactured according to the SPT9 or the BCDMOS standard and may lie in the range of 0 V to 60 V. Therefore, the filter resistor 104 and the filter capacitor 106 need to be implemented as high voltage components, i.e. be able to handle voltages in the respective range of the input signal provided at the circuit input 102. The microcontroller 108, on the contrary, may be implemented in CMOS technology and may include low voltage components. One disadvantage of the configuration shown in FIG. 1 may be the set of external components and their relatively large size, due to which an integration of these components directly into the integrated circuit is prevented.